Przeg!qd Geo!ogiczny, vo!. 45, nr 10, 1997
syntectonic Early Styrian phase (Early Badenian in age),
Late Styrian phase (EarlylLate Badenian) and the Attican
phase (Sarmatian-Pliocene?). During the first and second phases a gravitational stress field was acting together with small extension of NE-SW to E-W direction. At that time, the NW-SE orientated faults, which existed earlier in the Neogene basement, became reactivated. Due to a listric shape of the NW-SE fault surface, beds of footwalls were antithetically rotated. During the Attican phase stress field pattern was changed and a horizontal compression prevai-led. In the central part of the Carpathian Foredeep the compresion of N-S direction turned to NE-SW (30-50°) in the western part. Sinistral strike-slip faults of NE-SW and ENE-WSW directions were developed. The
complementa-ry shear fractures and a meridional pattern of master joints
were initiated in the horizontal compressional stress field. At the end of sinistral trunscurrent movements, the N-S extension (transtension) affected oblique character of many
main faults (i.e. the Kurdwan6w-Zawichost zone). All the structures were neotectonically renewed, especially during Valachian and Pasadenian phases. The evidence of neotec-tonic movements are deformations of the pre-glacial Wit6w gravels and of the Quaternary deposits and
morphostructu-res, as well. The magnitude of normal fault throws and of transcurrent displacements enable one to define the Late
Sty-rian and Attican phases as the main tectonic phases during the Neogene of the Carpathian Foredeep area. The otherregistered tectonic deformations - Early Styrian and neotectonics were formed due to a minor earthquakes and hydrotectonic pheno-mena - without stronger regional stress.
Quantifying effects of parameter variations on results of flexural
modelling of continental collision zones: Polish Outer Carpathians
Piotr Krzywiec
1&
Pawel T. J ochym2
1 Polish Geological Institute, Rakowiecka 4, 00-975 Warszawa, Poland
2 Institute of Nuclear Physics, Radzikowskiego 152, 31-342 Krak6w, Poland
Previously completed flexural modelling studies of the Polish Carpathian Miocene collision zone proved, that along the entire Polish segment ef this orogenic belt, subsurface loads
related to slab-pull mechanism were most important for its development. Also, it was concluded that there are significant variations of the effective elastic thickness (EET) of the foreland lithosphere along the Polish segment of the Carpathians. These modelling studies were based on several simplifying
assump-tions, like constant EET of the foreland lithospheric plate, lack of subsurface horizontal forces, etc. Such a model can serve as a first approximation of the continental collision zone.
In order to fully estimate influence of variations of all the parameters included in the model of thin elastic plate flexure, like: variations of flexural rigidity, horizontal sub-surface forces, irregularly distributed topographic loads, two point boundary conditions etc., a new modelling code was developed. The code is based on the concept of using nume-rical integration for finding solutions of the full flexural equation. This equation belongs to a very difficult class of
stiff equations. This type of equation could be solved by relaxation method. Two point boundary conditions are also handled effectively by this method. The numerical solution is consequently fitted to the data points by adjustments of coefficients in the equation. Best values of parameters are found by fitting with multidimensional down-hill simplex algorithm. With this procedure, it is possible to "free" or "fix" any parameter of the equation and select any desired set of parameters for fitting.
Our analysis of solutions produced by the above scheme shows that some parameters are more important then others.
There is also (rather unfortunate) effect of" complementary" parameters which could change a shape of the solution in the very similar way. Thus, it is difficult to find a precise value of such quantities. They act rather as a pair, and one can be used in place of another. The horizontal force and Moho density contrast is an example of such a pair of parameters. We have found that inhomogeneities of elastic properties of the plate could play a great role, and could greatly improve a solution with respect to "ideal" homogenous case. We have also found that distributed topographical loads could b_e of greater importance than highly localised loads, since the
influence of a localised force acting on the elastic plate is generally limited to the length of "flexural wave".
Two-dimensional models of petrophysical parameter distribution
in
structural-facies
units of Polish Outer Carpathians in the
Lupk6w-Jaroslaw profile
Jan Kusmierek
1,A.P. Lapinkiewicz
1,T. MackowskP, Michal Stefaniuk
2 IDepartment of Fossil Fuels, University of Mining andMe-tallurgy, Mickiewicza 30, 30-059 Krak6w, Poland
2 Department of General and Mathematical Geology,
Univer-sity of Mining and Metallurgy, Mickiewicza 30, 30-059 Krak6w, Poland
1084
The tectonics of the Cretaceous and Palaeogene flysch formations in the Lupk6w-Jaroslaw profile is characterised by elevated asymmetric folds and thrust sheets that are cut by overthrusts. Their deep geological structure was
data and borehole logs with the trends of thickness changes of stratigraphic complexes and the morphology of the pre-Alpine basement. The geometric model of folds and overt-hrusts was verified using a method of cross-section balancing.
The bulk density, resistivity and seismic wave velocity data from boreholes were set along the study profile. Bulk density data were supplemented by the results of density measurements in surface outcrops. Models of distribution of bulk density, resistivity and seismic velocity along the pro-file were constructed using the above mentioned data set, as well as data obtained from a structural-lithofacies cross-sec-tion. Two modes of petrophysical parameter evaluation were applied. The distribution of density, porosity and shaliness in cells of a finite-element net was determined in the central part of the profile by interpolating and extrapolating bore-hole data and using the STRATAMODEL program. Resisti-vities and seismic wave velocities for each cell were calculated using empirical relations between density, poro-sity and shaliness, and those parameters. Lithological diffe-rentiation along the profile was taken into account. The correctness of calculation results was verified using well logging data. Petrophysical data distribution was then ave-raged for respective lithostratigraphic complexes. The di-stribution of physical parameters of rocks was obtained
Przeglqd Geologiczny, vol. 45, nr 10, 1997
directly from interpolation and extrapolation of well logging and surface data for lithostratigraphic complexes in the outer parts of the profile.
As a result of calculation, cross-sections illustrating two-dimensional distribution of petrophysical parameters in structural-facies units were obtained. The flysch cover is characterised by great variations of physical parameters, caused by the variability of the flysch lithology. In general, the flysch formations are built of sequences of sandstone and shale layers of contrasting physical properties. A proportion between the volumes of these lithotypes determines avera-ged values of physical parameters and anisotropy coeffi-cients. The presence of other lithotypes, i.e. carbonate and siliceous rocks, strong tectonic deformation and lateral lit-hological alteration complicate the situation. Under such circumstances, the evaluation of trends of petrophysical parameter changes and establishing its connection with lithostratigraphic data is difficult. However, some general relationships could be observed.
The authors used the results obtained in projects No 9 0427 91 01 and 9 T12B 020 11 granted by the Committee for Scientific Research, and project No 100/SG/91 financed by the PGNiG GEONAFTA Warsaw.
Pre-Miocene tectonic events in the foreland of the Polish Carpathians
Jan Kutek
1IInstitute of Geology, University of Warsaw, Zwirki i Wigury 93,02-089 Warszawa, Poland
(1) A zone displaying distinctively great crustal thick-nesses, which comprises the Lublin Graben and the Radom-Krasnik Uplift in south-eastern Poland, and extends into the western Ukraine, can be interpreted as a result of Late Variscan (late Westphalian-early Rotliegendes) transpres-sional tectonics.
(2) The multi stage evolution of the Polish Permo-Meso-zoic Rift Basin dates back to the Permian (late Rotliegendes) in northern and central Poland, and to the Middle Jurassic south of the Holy Cross Mts Lineament. This evolution was terminated by the Laramide inversion of the proximal zone of this basin. The inversion gave rise to the Mid-Polish Anticlinorium, which extends from the Baltic Sea south-east across cratonic areas of Poland and the western Ukraine, plunging beneath the nappes of the Outer Carpathians.
Available evidence permits to interpret a vast area of cratonic Poland as belonging to the Polish Permo-Mesozoic Rift Basin, assuming a concept of asymmetrical rifting, with simple shear involved. According to such an interpretation, the Mid-Polish Anticlinorium corresponds but to the
proxi-mal zone of the Polish Rift, whereas regions situated further south-west (e.g., the Szczecin-L6dz- Miech6w Depres-sion, the Fore-Sudetic and Cracow-Silesian Monoclines, the Upper Silesian Coal Basin and the Opole Depression) rep-resent more distal portions of the rift basin.
(3) The southernmost (peri-Carpathian) portion of the Polish Rift Basin roughly coincides with the Meta-Carpat-hian Arch, a zone of uplift or lesser subsidence that separated the Central European Basin from basins of the Carpathian Domains in Permian, Mesozoic and Cenozoic times. An exception to this rule is the strong subsidence that affected the arch in the Late Jurassic. Presumably, the development of the Meta-Carpathian Arch should be interpreted in terms of crustal or litho spheric folding.
(4) The formation of the Mid-Polish Anticlinorium, with some dextral strike-slip movements involved, was chiefly a Laramide event, culminating in the Paleocene. Still contro-versial is the evidence for an earlier commencement of the development of this anticlinorium in mid-Late Cretaceous time, but a discrete Subhercynian event (of extensional nature ?), centered over the Coniacian, can be recognized in the Cracow region, beyond the Mid-Polish Anticlinorium.
